1. Field of the Invention
The present invention relates to an electrodeless lighting apparatus and, more particularly, to an electrodeless lighting apparatus capable of varying its length and aperture ratios corresponding to its parts according to a change in surrounding conditions.
2. Description of the Background Art
In general, an electrodeless lighting apparatus is a device capable of effectively supplying light without an electrode as microwave generated from a microwave generator allows buffer gas inside a bulb to be in a plasma state and metal compound to continuously diffuse light. The electrodeless lighting apparatus has a longer life span and more excellent lighting effects than a general incandescent lamp or fluorescent lamp.
FIG. 1 is a longitudinal sectional view illustrating one example of a lighting apparatus using microwave energy in accordance with a conventional art.
A conventional lighting apparatus using a microwave energy, as shown in FIG. 1, includes a case 1 forming a predetermined internal space, a magnetron 2 mounted inside the case 1 and generating microwave, a high voltage generator 3 increasing general AC power to a high voltage and supplying it to the magnetron 2, a waveguide 4 for guiding microwave generated from the magnetron 2, a resonator 6 installed at an outlet 4a of the waveguide 4 in order to communicate with the waveguide 4, and having a mesh structure by which leakage of microwave is prevented but light is allowed to pass therethrough and a bulb 5 located inside the resonator 6 and generating light as an enclosed material becomes plasma by a microwave energy transmitted through the waveguide 4.
The lighting apparatus using microwave also includes a reflector 7 formed at a front side of the case 1, that is, at a neighboring region of the resonator 6, to concentratively reflect light generated from the bulb 5 forward.
A dielectric mirror 8 is installed in the outlet 4a of the waveguide 4 in order to allow microwave transmitted through the waveguide 4 to pass therethrough and light emitted from the bulb 5 to be reflected forward, and a hole 8a is formed at the center of the dielectric mirror 8 to allow a shaft portion 9 of the bulb 5 to penetrate therethrough.
A cooling fan assembly 10 for cooling the magnetron 2 and the high voltage generator 3 is provided at the rear of the case 1. Reference numeral 10a denotes a fan housing, 10b denotes a blowing fan, M1 denotes a bulb motor, and M2 denotes a fan motor.
The conventional lighting apparatus using microwave is operated as follows.
When a driving signal is inputted to the high voltage generator 3, the high voltage generator 3 increases AC power and supplies the increased high voltage to the magnetron 2. Then, oscillated by the high voltage, the magnetron 2 generates microwave having a very high frequency. The thusly generated microwave is guided through the waveguide 4 and radiated into the resonator 6 through a slot portion 4b formed at the inner side of the outlet 4a of the waveguide 4. The microwave radiated into the resonator 6 discharges a material enclosed in the bulb 5 to generate light having a specific spectrum, and as this light is reflected forward by the reflector 7 and the dielectric mirror 8, a lighting space becomes illuminated.
However, the conventional electrodeless lighting apparatus can maintain high light efficiency only when the length (or volume) of the resonator and an aperture ratio of mesh are changed if a distance between the outlet of the waveguide and the center of the bulb needs to be lengthened because of a change in the surrounding environment such as a change in color of the bulb or lateral lighting. In this case, since the resonator itself must be changed each time according to required conditions, a resonator whose length and aperture ratio vary according to the applied conditions is manufactured. Accordingly, manufacturing time and costs are excessively spent, and part of a system must be re-assembled in order to change the resonator.